September in the Vegetable Garden: The Beginning of the End

In many New England gardens, early September is when the harvest season begins in earnest. While August gardens supply a trickle of tomatoes, cucumbers, and summer squash, the first week of September turns the spigot wide open. Suddenly the garden overflows with these crops as well as tomatillos, carrots, onions, leeks, and the first potatoes. Cucumber vines crawl through rows of bush beans as they crank up their yield, and winter squashes grow on vines weaving through corn stalks with ripening ears.

The cool nights of September bring a touch of melancholy as the end of another garden year nears. Leaves on the tomato plants turn yellow, then a dry brown, leaving ripe tomatoes clinging to near naked stems. Annuals in pots scattered among the garden beds cease flowering while their foliage withers. Thus with each September day that passes, vegetable garden work includes harvests for the compost pile.

Composting Plants Infected with Powdery Mildew

This has been a good year for the powdery mildew fungus, a perfect storm for gardeners growing cucumbers and squash. High humidity, cloudy days, and dense plant growth have all contributed to a plague of powdery mildew on the cucumber plants in Marjorie’s Garden, an infection so severe that I have decided to take them out in favor of early September sowings of spinach and other leafy greens.

Powdery mildew is a common late summer fungus disease on winter squash, including pumpkins.

Powdery mildew is a common late summer fungus disease on winter squash, including pumpkins.

Can you compost powdery mildew-infected cucurbit plants? For Maine gardeners, the answer is yes. The mildew spores do not survive the winter in Maine, so chop up the leaves and stems and mix them deep into the heart of the compost pile where temperatures are hottest. Any that are not killed by the high temperatures will likely succumb to the cold temperatures of winter when the entire compost pile turns to ice. And should a few powdery mildew spores survive, they can join the billions introduced on summer winds from more southerly areas.

Early September Sowings

Seeds of leafy vegetables, including lettuce, spinach, arugula, mizuna, tatsoi, and pak choy, can be sown in early September to be harvested through fall and into early winter when covered with a layer of poly. We grow these crops in raised beds equipped with PVC hoops to support the covering. The 1/2-inch hoops fit into sections of one inch PVC pipe mounted to the inside walls of the bed frame.

Last year's Last year's late-summer-sown basil crop survived the frosts of last fall under a layer of poly supported by PVC hoops.

Last year’s late-summmer-sown basil crop survived the frosts of late fall under a layer of poly supported by PVC hoops.

To keep the seed beds moist, I cover them with sheets of row cover material, holding the lightweight fabric down with hefty stones placed on the bed edges. This is the same material used to exclude insect herbivores from sensitive crops and can be left on the beds after germination if you allow sufficient slack in the fabric for growth of the seedlings. Water from rain or irrigation easily passes through the fabric while evaporation is significantly slowed.


Potatoes to be stored should not be dug until their tops have died and dried. They can even be left in the ground for a few weeks after the tops have died, if necessary. Dig the tubers carefully to avoid bruises and cuts, setting any damaged potatoes aside for immediate use. Do not wash or scrub potatoes intended for storage, but carefully brush off the excess soil.

Once dug, potatoes need to be cured for a week or two in a warm (60 to 75° F), moist, dark location. We use a corner of our basement, laying the tubers in single layers on wire racks. Curing will help heal any minor wounds on the tubers.

Once cured, potatoes are best stored in a cooler location with temperatures near 45° F. This is difficult to achieve in most homes (unless you have an extra refrigerator), so pick the coolest corner of the basement, a location that is also humid and dark. The closer you get to these temperature and humidity requirements, the longer the potatoes will keep.

Winter Squash and Pumpkins

Avoid frost on the pumpkins! If winter squash, including pumpkins, are to keep in storage, they should be harvested before being exposed to frost. Harvest them when their rinds have hardened and the fruits have developed a deep, solid color. Leave about 3 inches of stem attached to pumpkins and 2 inches attached to other winter squash. Do not try to store a squash if the stem has been completely removed.

Cure pumpkins and winter squash at 80 to 85° F for seven to ten days, then store in a dry, well-ventilated location with temperatures near 55° F (45° F for acorn squash). In olden days, gardeners would store winter squash beneath their beds.


Harvest carrots for storage in late fall, before the soil freezes, and while the soil is dry. Cut off the tops to within ½ inch of the root. Soil can be removed with a quick rinse, but the carrots should not be scrubbed.

Once dry, place the carrots in plastic bags perforated with small holes, and store them in a cold (32 to 40° F), humid location. Carrots can also be stored in the garden by placing a deep layer of straw mulch over the plantings as the weather gets cold but before the ground freezes.


Leeks, like those that line the edges of this bed, should be harvested for storage in early winter, before the ground freezes.

Leeks, like those that line the edges of this bed, should be harvested for storage in early winter, before the ground freezes.

Summer leek varieties that are intended for harvest in the fall, such as ‘King Richard’ and ‘Tadorna Blue,’ are best left in the ground and harvested as needed until the first frost. They can be kept in the ground even longer if they are covered with a thick layer of straw or shredded leaves. At some point, however, before a hard freeze, you will want to dig the leeks still in the garden bed and prepare them for indoor winter storage in the following manner.

Place 2 to 3 inches of a damp medium such as peat, clean sand, or sawdust in a 5-gallon bucket or large tub. Do not get the medium too soggy, or it will cause the leeks to rot. Stand the leeks with their roots on the medium and push them down to establish good contact between the roots and medium. The roots do not need to be completely covered, just firmly in touch with the medium.

Stored in this manner, the leeks will continue to grow, very slowly, rather than going totally dormant. Trim the tops a bit and store the bucket or tub in a cool dark place with some humidity, checking the medium occasionally to make sure it stays moist. Do not remove any of the outer leaves until you use the leeks.

Sow Oats Wherever Soil Is Bare

We prefer oats as a cover crop, sowing them in September wherever the soil would otherwise remain bare. The seeds quickly sprout, and by October the sown beds are covered in a green blanket. Roots of the oat plants grow deep into the soil, mining nutrients to feed the growing shoots.

Unlike winter rye, oats will winter-kill and you can dig in the mat of dead leaves as soon as the soil can be worked in spring, then wait two weeks before planting. Or, if you are in a hurry to sow peas, you can move the mat of grass leaves aside, sow the seeds in rows, and use the oat leaves as mulch between the rows.

Sow oat seeds at the rate of 2 pounds per 1,000 square feet. Sow the seeds as early as possible, for the sooner a cover crop is planted, the more organic matter it will produce for incorporating into the soil in spring.

I rise early on September morns, taking my cup of coffee to the porch to plan the day while the sun rises and takes the chill from the air. I work slowly in the garden through the morning, taking extended breaks to walk around. Soon enough it will all be gone.

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About Reeser Manley

I was born in Laramie Wyoming but moved to the southeast at an early age. I was educated through my B.S. in Biology in the Columbus, Georgia area, then crossed the Chattahoochee River to earn my M.S. in Botany at Auburn University. For the next ten years, I worked as Horticultural Manager for the George W. Park Seed Co. in Greenwood, S.C. At 40 years of age, I decided to return to graduate school and in 1994, I earned a Ph.D. in Horticultural Science from Washington State University, Pullman, Washington. Fast forward through 10 years at university (7 at UMaine, Orono) and you find me teaching high school science in Eastport, Maine, the edge of the world, and writing a weekly garden column for the Bangor Daily News. My new book, The New England Gardener's Year, a Month-by-Month Guide for Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, and Upstate New York”, will be published later this year by Cadent Publishing. You can learn more about the book by visiting its Facebook page: